High-frequency semiconductor device

ABSTRACT

A high-frequency semiconductor device is provided with a ceramic substrate, an element group including semiconductor elements and passive components mounted onto a bottom portion of the ceramic substrate, and a composite resin material layer formed on the bottom portion of the ceramic substrate so as to bury the element group. The composite resin material layer is formed by a composite resin material including an epoxy resin and an inorganic filler material, and has a flat bottom surface on which electrodes for connecting to the outside are formed. As packaging of a structure in which the receiving system and the transmitting system are formed in a single unit, such as an RF module, the high-frequency semiconductor device achieves a small size, a high mounting density, and excellent heat release properties.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to structures for high-frequencysemiconductor devices on which high-frequency semiconductor elements,control integrated circuit elements, and surrounding circuits aremounted, and in particular to packaging structures thereof.

[0003] 2. Description of the Related Art

[0004] There is an increasing demand for high-frequency semiconductordevices employed primarily in mobile communications equipment, such asportable telephones, as “all-in-one” RF modules with receiving andtransmitting systems formed into a single unit. According to suchsituation, a need has arisen for a reduction in packaging size, underthe condition that the number of semiconductor elements and chipcomponents that are mounted increases due to the provision ofhigh-frequency semiconductor elements, control integrated circuitelements and surrounding circuitry in order to incorporate receiving andtransmitting systems into a single unit.

[0005] A conventional example of a high-frequency semiconductor deviceis described with reference to FIG. 10. In FIG. 10, numeral 1 denotes asemiconductor element of a chip form such as a transistor and 2 denotesa ceramic multilayer substrate. Numeral 3 denotes chip components suchas chip resistors, chip capacitors, and chip inductors. Numeral 4denotes bottom electrodes, 5 denotes metal wires, 6 denotes pottingresin, and 7 denotes a metal cap.

[0006] Component mounting lands for mounting the semiconductor element 1and the chip components 3 and an electrode wiring pattern (not shown)are formed on the surface of the ceramic multilayer substrate 2 throughscreen printing or metal thin film etching, for example. Thesemiconductor element 1 is die bonded to the component mounting landportion on the ceramic multilayer substrate 2, and connected to theelectrode wiring pattern that is formed on the surface of the ceramicmultilayer substrate 2 by the metal wires 5. The semiconductor element 1and the metal wires 5 are covered by the potting resin 6. The chipcomponents 3 are mounted to predetermined locations by soldering. Themetal cap 7, which forms the packaging, is attached to the ceramicmultilayer substrate 2. The electrode wiring pattern on the surface ofthe ceramic multilayer substrate 2 is connected electrically to thebottom electrodes 4 via through holes, which are not shown, that passthrough the ceramic multilayer substrate 2.

[0007] However, with structures where semiconductor elements and chipcomponents are simply mounted onto the ceramic multilayer substrate 2,as is the case with the conventional high-frequency semiconductor devicedescribed above, the desired reduction in the packaging size cannot bemet sufficiently as the number of installed components increases.

[0008] Also, the semiconductor chip provided on the ceramic multilayersubstrate is a heat-generating element such as a power amplifier, andthus all the heat generated from the semiconductor chip is transferredto the bottom portion via the ceramic multilayer substrate and releasedfrom the bottom portion electrodes. However, the ceramic multilayersubstrate has a high thermal resistance. This led to the problem of notenough heat being released from the semiconductor chip, which consumes alarge amount of power, and the semiconductor chip becoming hot.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide ahigh-frequency semiconductor device in which receiving and transmittingsystems including active elements such as semiconductor elements likepower amplifiers and switches or semiconductor elements for control, andpassive components such as resistors, capacitors, inductors, andfilters, are mounted as a single unit in a layered substrate, so as toimprove electrical properties by reducing impedance due to the reductionin the wiring length, reducing the floating capacity, and improvinganti-noise properties, and to provide a smaller size device withimproved heat release properties.

[0010] A high-frequency semiconductor device of the present embodimentis provided with a ceramic substrate, an element group includingsemiconductor elements and passive components mounted onto a bottomportion of the ceramic substrate, and a composite resin material layerformed on the bottom portion of the ceramic substrate so as to bury theelement group. The composite resin material layer is formed of acomposite resin material including an epoxy resin and an inorganicfiller material, and has a flat bottom surface on which electrodes forconnecting to the outside are formed.

[0011] With this configuration, the semiconductor elements and passivecomponents are mounted on the bottom portion of the ceramic substrate,so that the bottom surface of the substrate can be utilized as themounting area and the mounting density can be increased. Also, byburying the element group in the composite resin material layer, anincrease in reliability, such as mechanical resistance and resistanceagainst moisture, can be achieved. Moreover, by making the bottomsurface of the composite resin material layer flat and providing theelectrodes for connecting to the outside, the product is easilytransported and handled, and the ability to mount the high-frequencysemiconductor device as a module is improved.

[0012] It is preferable that the semiconductor elements are mounted byflip-chip connection. Thus, a drop in impedance due to the reduction inwiring length, a reduction in the floating capacity, an increase in themounting density, and reduction in the height of the packaging can beachieved.

[0013] The high-frequency semiconductor device mentioned above can begiven a structure where interlayer connector structures are formed inthe composite resin material layer, the interlayer connector structuresbeing filled with a high thermal conductivity resin material havingthermal conductivity higher than that of the epoxy resin, the electrodesfor connecting to the outside include a ground electrode that functionsas a heat release electrode, and the surface of the semiconductorelement is connected to, the ground electrode via the interlayerconnector structures. Thus, heat generated by the semiconductorelements, which are heat-generating elements such as power amplifiersand mounted by flip-chip connection, can be adequately released from theelectrodes for connecting to the outside via the interlayer connectorstructures provided in a single or a plurality of locations.

[0014] Another high-frequency semiconductor device of the presentinvention is provided with a first ceramic substrate having a circuitpattern, a second ceramic substrate on which semiconductor elements aremounted, and a composite resin material layer that buries thesemiconductor elements and is provided between the first ceramicsubstrate and the second ceramic substrate. The composite resin materiallayer is formed by a composite resin material including an epoxy resinand an inorganic filler material, interlayer connector structures inwhich a conducting resin material has been filled are formed in thecomposite resin material layer, and the circuit pattern of the firstceramic substrate and a circuit pattern of the second ceramic substrateare electrically connected via the interlayer connector structures.

[0015] According to this configuration, the first ceramic substrate andthe second ceramic substrate are employed according to the electrical,thermal, and mechanical properties that are required, and are depositedwith the composite resin layer interposed between them, so that a smallsize substrate packaging can be formed. Even if the linear expansioncoefficients of the first ceramic substrate and the second ceramicsubstrate are different, a highly reliable packaging that absorbs thisdifference can be provided, because the composite resin layer isinterposed between the substrates. In addition to the fact thatsemiconductor elements and passive component can be mounted between thefirst ceramic substrate and the second ceramic substrate, it is alsopossible to mount components on the upper surface of the firstsubstrate, and thus the overall mounting density of the product can beincreased. Moreover, by burying the semiconductor elements, for example,with the composite resin, reliability such as mechanical resistance andresistance against moisture can be increased.

[0016] In this configuration, it is preferable that the semiconductorelements provided on the second ceramic substrate have been mounted byflip-chip connection. Thus, the thickness of the composite resinmaterial layer between the first ceramic substrate and the secondceramic substrate can be reduced. Also, a drop in impedance due to thereduction in wiring length, a reduction in the floating capacity, anincrease in the mounting density, and a reduction in the packagingheight can be achieved.

[0017] Additionally, it is possible to adopt a configuration in which atleast one of the semiconductor elements provided on the second ceramicsubstrate is connected by metal wires. Thus, those elements of thesemiconductor elements that are mounted onto the second ceramicsubstrate for which the release of heat is required can be adhered by ahigh conductivity adhesive agent and connected to the substrate by themetal wire, so that heat can be dissipated from those elements directlyto the second ceramic substrate. This configuration is particularlyeffective when a large amount of heat is generated by the semiconductorelements.

[0018] In this configuration, the surroundings of the semiconductorelements provided on the second ceramic substrate and connected by themetal wire can be sealed by a liquid epoxy resin. Thus, stress that isapplied to the semiconductor elements and the metal wire when the firstceramic substrate and the second ceramic substrate are adhered by thecomposite resin material can be alleviated, so that defects such as thewire falling over or being disconnected can be eliminated, and theassembly yield can be increased. Moreover, the epoxy resin that sealsthe semiconductor elements can be employed as a spacer for the firstceramic substrate and the second ceramic substrate, so that the gapbetween the two substrates can be adjusted.

[0019] A further high-frequency semiconductor device according to thepresent invention is provided with a ceramic substrate having a cavityportion in its bottom portion, an element group including semiconductorelements and passive components mounted to the bottom portion of thecavity portion, a composite resin material layer formed so as to burythe element group in the cavity portion, and electrodes for connectingto the outside that are formed on a bottom portion of the ceramicsubstrate other than at the cavity portion. The composite resin materiallayer is formed by a composite resin material including an epoxy resinand an inorganic filler material, and a bottom portion of the compositeresin material layer is flat in shape.

[0020] As in the configuration mentioned above, this configurationachieves an increase in the mounting density, an increase in devicereliability such as in the mechanical resistance and in the resistanceagainst moisture, and an increase in mountability. Additionally, thecomposite resin material layer can easily be formed by filling acomposite resin material into the cavity portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a cross-sectional view showing a high-frequencysemiconductor device according to Embodiment 1 of the invention.

[0022]FIG. 2 is a perspective view of the high-frequency semiconductordevice of FIG. 1 seen from its rear side.

[0023]FIG. 3 is a cross-sectional view showing a high-frequencysemiconductor device according to Embodiment 2 of the invention.

[0024]FIG. 4 is a cross-sectional view showing a high-frequencysemiconductor device according to Embodiment 3 of the invention.

[0025]FIG. 5 is a perspective view of the high-frequency semiconductordevice of FIG. 4 seen from its rear side.

[0026]FIG. 6 is a cross-sectional view showing a high-frequencysemiconductor device according to Embodiment 4 of the invention.

[0027]FIG. 7 is a cross-sectional view showing a high-frequencysemiconductor device according to Embodiment 5 of the invention.

[0028]FIG. 8 is a cross-sectional view showing a high-frequencysemiconductor device according to Embodiment 6 of the invention.

[0029]FIG. 9 is a cross-sectional view showing a high-frequencysemiconductor device according to Embodiment 7 of the invention.

[0030]FIG. 10 is a cross-sectional view showing a conventional exampleof a high-frequency semiconductor device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] First Embodiment

[0032]FIG. 1 is a cross-sectional view of a high-frequency semiconductordevice according to Embodiment 1 of the present invention. FIG. 2 is aperspective view of the high-frequency semiconductor device of FIG. 1seen from its rear side.

[0033] In FIG. 1, the numeral 1 a denotes a gallium-arsenide powersemiconductor element serving as a power amplifier, 1 b denotes agallium-arsenide semiconductor element serving as a switching element,and 1 c denotes a silicon semiconductor element for circuit control.Numeral 2 denotes a non-shrinkage ceramic multilayer substrate, whichincorporates in its inner layers printed resistors 8 and printedcapacitors 9 formed by printing a paste material that includes metal,and which may be formed by baking at a low temperature. Numeral 3denotes a chip component such as, for example, a chip capacitor forfine-tuning the high-frequency circuit constants. Numeral 5 denotesmetal wires, and 10 denotes a composite resin material layer includingan epoxy resin and an inorganic filler such as silica. Numeral 4 denoteselectrodes for connecting to the outside which may be made of aconductor formed on the bottom surface of the composite resin materiallayer 10. Numeral 11 denotes a plurality of interlayer connector viaholes formed in the composite resin material layer 10 and functioning asan interlayer connector structure, and numeral 12 denotes a conductingresin buried in each interlayer connector via hole 11.

[0034] Although not shown in the drawings, an electrode wiring patternand a component mounting land for mounting the chips of thesemiconductor elements 1 a, 1 b, and 1 c and the chip component areformed on the bottom surface of the ceramic multilayer substrate 2 byscreen printing or metal thin film etching. The gallium-arsenide powersemiconductor element 1 a, the gallium-arsenide semiconductor element 1b, and the silicon semiconductor element 1 c may be die bonded to thecomponent mounting land portion on the bottom surface of the ceramicmultilayer substrate 2 by soldering, for example, and are connected withthe metal wires 5 to the electrode wiring pattern that is formed on thebottom surface of the ceramic multilayer substrate 2. In addition,although not shown in the drawings, a plurality of passive componentssuch as chip resistors, chip capacitors, and chip inductors may befastened and connected by soldering or the like to the circuit patternthat is formed on the bottom surface of the ceramic multilayer substrate2.

[0035] The chip dimensions of the semiconductor elements 1 a, 1 b, and 1c are ordinarily 1.6 mm×0.6 mm and 100 μm thickness for the poweramplifier element; 0.8 mm×0.6 mm and 150 μm thickness for the switchingelement; and 1.0 mm×0.7 mm and 300 μm thickness for the control element.

[0036] The semiconductor elements 1 a, 1 b, 1 c and the passive elementsare buried by the composite resin material layer 10. As shown in FIG. 2,the bottom portion of the composite resin material layer 10 is flat andserves as a flat electrode surface. Moreover, as shown in FIG. 1, theplurality of the interlayer connector via holes 11 are formed in thecomposite resin material layer 10, and conducting resin 12 is filledinto the interlayer connector via holes 11. The interlayer connector viaholes 11 match the position of the electrodes 4 for connecting to theoutside.

[0037] The interlayer connector via holes 11 act both to contact thecircuit pattern that is formed on the bottom surface of the ceramicmultilayer substrate 2 with the electrodes 4 for connecting to theoutside, and to release heat that is generated by the semiconductorelements 1 a, 1 b, and 1 c via the ceramic multilayer substrate 2. Thevia holes may have a diameter of 200 μmφ and are filled with acopper-based paste serving as the conducting resin 12. An electrodewiring pattern may be formed on the upper surface of the ceramicmultilayer substrate 2, and a plurality of chip components 3, such aschip resistors, chip capacitors, and chip inductors, may be fastened andconnected to the electrode pattern on the upper surface by soldering orthe like.

[0038] The high-frequency circuit constant is determined by the passiveelements that are buried by the composite resin material 10 and theprinted resistors 8 and the printed capacitors 9, which are formedbetween the layers of the ceramic multilayer substrate 2, and thehigh-frequency circuit constant is fine-tuned at each high-frequencysemiconductor device with the chip components 3 that are connected tothe upper surface of the ceramic multilayer substrate 2. Also, althoughnot shown in the drawings, the electrode pattern formed on the uppersurface of the ceramic multilayer substrate 2, the printed resistors 8,the printed capacitors 9, the electrode pattern formed between thelayers of the ceramic multilayer substrate 2, and the electrode patternformed on the bottom surface of the ceramic multilayer substrate 2 areelectrically connected to one another via through holes that passthrough the ceramic multilayer substrate 2, as appropriate.

[0039] The thickness of the composite resin material layer 10 isdetermined by the height of the semiconductor elements and the passivecomponents that are mounted. Here, this value can be slightly above orbelow the standard for the thickness at the semiconductor elements 1 a,1 b, and 1 c, which is the wire loop height of the metal wire 5 plus 300μm, or the standard for the thickness at the passive components, whichis the component height plus 300 μm.

[0040] The ceramic multilayer substrate 2 can be formed by using analumina substrate (high temperature cofired ceramics (HTCC) substrate),a low temperature cofired ceramics (LTCC) substrate, and so on.Generally, the “alumina substrate” means the HTCC substrate. Both ofthem contain alumina as a main component and the content thereof ishigher in HTCC than in LTCC. Cofiring temperature is 1300° C. to 1500°C. for HTCC and 800° C. to 900° C. for LTCC.

[0041] The composite resin material layer 10 may be formed by using, forexample, a sheet obtained by mixing epoxy resin with 70 to 80% by weightof an inorganic filler material (mainly silica), coupling agent,pigment, solvent, etc., kneading them, and forming into a sheet withuniform thickness. The coupling agent adheres to the inorganic fillermaterial and increases wettability of the inorganic filler material withrespect to the epoxy resin. In order to couple the composite resinmaterial layer 10 to the ceramic multilayer substrate 2 as shown inFIGS. 1 and 2, the composite resin material layer 10 is superposed onthe ceramic multilayer substrate 2 with chips mounted and they aresubjected to hot-pressing to be formed.

[0042] The composite resin material layer 10 may be formed also by usinga solventless sheet in which a solvent is not added. In such case thesheet is made of a liquid epoxy resin with an inorganic filler material(mainly silica) added.

[0043] As the conducting resin 12, Ag paste (adhesive resin with silveradded as a filler) may be used generally. The composite resin materiallayer 10 is subjected to punching to form holes and then Ag paste isfilled into the holes by a printing method. When the composite resinmaterial layer 10 and the ceramic multilayer substrate 2 with chipsmounted are superposed with each other and subjected to hot-pressing tobe formed, Ag paste is cured together with the composite resin materiallayer 10. Also Cu paste may be used as the conducting resin 12. Howeverit is oxidized easily compared to Ag paste.

[0044] In the foregoing description, silica was used as an example ofthe inorganic filler for the composite resin material layer 10, but thefiller material can be chosen according to properties that are required.For example, if high heat-release properties are required, then aluminacan be used as the filler material, which would permit adequate heatrelease.

[0045] The electrodes 4 for connecting to the outside that are formed onthe rear surface of the composite resin material layer 10 have a flatrear surface, and thus as a module, the high-frequency semiconductordevice easily can be transported and handled during manufacturing andinstalled by the user.

[0046] Embodiment 2

[0047] Embodiment 2 of the present invention is described with referenceto the cross-sectional view of the high-frequency semiconductor deviceshown in FIG. 3.

[0048] The device of FIG. 3 differs from that according to Embodiment 1shown in FIG. 1 in that the gallium-arsenide power semiconductor element1 a, the gallium-arsenide semiconductor element 1 b, and the siliconsemiconductor element 1 c are flip-chip connected on the circuit patternon the bottom surface of the ceramic multilayer substrate 2 via bumps 13having a metal core.

[0049] The bumps 13 are formed through SBB (stud ball bonding) usinggold wire, and maintain a gap of approximately 40 μm between thesemiconductor elements 1 a, 1 b, and 1 c and the ceramic multilayersubstrate 2. Other techniques that can be employed to provide the bumps13 include a technique employing plating around a copper core materialserving as the core and adhering with a conductive resin, a techniqueemploying an ACF (anisotropic conductive film), and a techniqueemploying a soldering material. Any of these techniques can be employedto achieve the same effect. Compared to the case in which thesemiconductor elements 1 a, 1 b, and 1 c are fastened to the substrateand they are connected by the metal wire, the height after installationcan be reduced by approximately one half. In this embodiment, thestandard for the thickness of the composite resin material layer 10after sealing is the chip height plus 300 μm.

[0050] When the semiconductor elements are flip-chip mounted onto thebottom surface of the ceramic substrate in this way, they can bedisposed in closer proximity to one another than when connected on thesubstrate via metal wiring, and components can be installed on the uppersurface of the substrate as well, so that the installation density ofthe entire product is increased.

[0051] Moreover, electrical property effects such as a lower impedancedue to the reduced wiring length and a reduction in the floatingcapacity also may be achieved.

[0052] Embodiment 3

[0053] Embodiment 3 of the invention is described in reference to thecross-sectional view of the high-frequency semiconductor device shown inFIG. 4 and the perspective view of the device of FIG. 4 seen from itsrear side shown in FIG. 5.

[0054] The device of FIG. 4 differs from that according to Embodiment 2shown in FIG. 3 in that interlayer connector via holes 21 are formeddirectly below the gallium-arsenide power semiconductor element 1 a,which is a power amplifier, and a heat-release electrode 14 is formed onthe bottom surface of the composite resin material layer 10 in alignmentwith the positions of the interlayer connector via holes 21. As shown inFIG. 5, a plurality of electrodes 4 for connecting to the outside andthe heat release electrode 14, which has a larger area than theelectrodes 4 for connecting to the outside, are formed on the bottomsurface of the composite resin material layer 10. Accordingly, heat canbe released effectively from the electrode of the gallium-arsenlidepower semiconductor element la via the interlayer connector via holes21. The heat release electrode 14 also serves as a ground electrode, andsuitably grounds the high-frequency semiconductor element to the groundpotential.

[0055] The diameter of the interlayer connector via holes 21 can besuitably chosen within a range of 150 μmφ to 500 μmφ. A single or aplurality of via holes 21 can be formed in correspondence with the chipsize of the gallium-arsenide power semiconductor element 1 a. In oneexample, a high thermal conductivity resin 22 is filled into the viaholes 21. The high thermal conductivity resin 22 has thermalconductivity higher than that of epoxy resin. Similar effects can alsobe achieved by filling into the via holes 21 the conductive resin 12that is used in the interlayer connector via holes 11.

[0056] One example of the high thermal conductivity resin 22 is composedof epoxy resin with 80 to 90% by weight of alumina added as a filler.Thermal conductivity thereof is more than 3 W/m·K. It may be filled intothe via holes 21 formed in the composite resin material layer 10 by aprinting method.

[0057] According to this embodiment, when the semiconductor element is aflip-chip mounted power device that generates a large amount of heat,the heat from the semiconductor can be suitably dissipated.

[0058] Embodiment 4

[0059] Embodiment 4 of the present invention is described with referenceto the cross-sectional view of the high-frequency semiconductor deviceshown in FIG. 6. The high-frequency semiconductor device according tothis embodiment has a structure in which the ceramic multilayersubstrate 2 (first substrate) and an alumina substrate 32 (secondsubstrate) sandwich the composite resin material layer 10, and in thisstate are adhered to one another to form a single unit.

[0060] The ceramic multilayer substrate 2 may be a non-shrinkagesubstrate formed through baking at low temperatures, and incorporates inits inner layers a printed resistor 8 and printed capacitors 9 formed byprinting a paste material that includes metal. The alumina substrate 32is a substrate on which gallium-arsenide semiconductor elements 1 a and1 b, such as power amplifiers and switches, and a silicon semiconductorelement 1 c for circuit control have been flip-chip mounted.

[0061] Via holes 11 for electrically connecting the ceramic multilayersubstrate 2 and the alumina substrate 32 are formed in the compositeresin material layer 10, and the conducting resin 12 is filled into thevia holes 11. The via holes 11 may have a diameter of 200 μm and arefilled with a copper-based paste. Although not shown, through holes areprovided in the alumina substrate 32 so as to electrically connect theelectrodes 4 for connecting to the outside and the heat releaseelectrode 14 to the electrode pattern on the surface of the aluminasubstrate 32.

[0062] Thus, by using the composite resin material layer 10 to adherethe plurality of substrates 2 and 32, the problem of peeling, forexample, due to differences in the linear expansion coefficient iseliminated, and because the semiconductor elements 1 a, 1 b, and 1 c areincluded in the adhesion layer, the component mounting density, themechanical resistance, and the resistance against moisture are improved.

[0063] Embodiment 5

[0064] Embodiment 5 of the present invention is described in referenceto the cross-sectional view of the high-frequency semiconductor deviceshown in FIG. 7.

[0065] The device in FIG. 7 differs from that according to Embodiment 4shown in FIG. 6 in that, of the semiconductor elements that are providedon the alumina substrate 32, the gallium-arsenide power semiconductorelement 1 a, which is for example a power amplifier and requires therelease of heat, is adhered by a high thermal conductivity adhesiveagent (not shown), and is connected to the alumina substrate 32 by themetal wire 5. Thus, heat can be released from the gallium-arsenide powersemiconductor element 1 a directly to the alumina substrate 32. Adheringthe element directly onto the alumina substrate 32 results in a largeheat transfer effect, and the further effect of releasing heat via themetal wire 5 can be observed. This embodiment is particularly effectivewhen a large amount of heat is generated by an element.

[0066] Embodiment 6

[0067] Embodiment 6 of the present invention is described in referenceto the cross-sectional view of a high-frequency semiconductor deviceshown in FIG. 8. The device of FIG. 8 differs from that according toEmbodiment 5 shown in FIG. 7 in that before the ceramic multilayersubstrate 2 and the alumina substrate 32 are adhered via the compositeresin material layer 10, the circumference of the gallium-arsenide powersemiconductor element 1 a and the metal wire 5 for connection that aredisposed on the alumina substrate 32 is sealed by a liquid epoxy resin6.

[0068] The amount of epoxy resin 6 can be enough to entirely cover thepower semiconductor element 1 a and the metal wire 5, and consideringthe resin spread when the epoxy resin 6 is cured, a highly thixotropicresin can be chosen as the epoxy resin 6. Thus, when the ceramicmultilayer substrate 2 and the alumina substrate 32 are adhered via thecomposite resin material layer 10, the stress to the semiconductorelement 1 a and the metal wire 5 can be alleviated, so that defects suchas the metal wire falling down or being disconnected are avoided and theassembly yield can be increased. Also, the epoxy resin 6 for sealing thesemiconductor element 1 a can be utilized as a spacer between theceramic multilayer substrate 2 and the alumina substrate 32, so that thegap between these substrates can be adjusted.

[0069] Embodiment 7

[0070] Embodiment 7 of the present embodiment is described in referenceto the cross-sectional view of the high-frequency semiconductor elementshown in FIG. 9. The device of FIG. 9 differs from that according toEmbodiment 2 shown in FIG. 3 in that the ceramic multilayer substrate 2has a cavity portion 2 a in its bottom surface, in which thesemiconductor elements 1 a, 1 b, and 1 c and the passive components areprovided, and the electrodes 4 for connecting to the outside are formedon the ceramic multilayer substrate 2 at portions peripheral to thecavity portion 2 a. The composite resin material layer 10 is formed inthe cavity portion 2 a, and the semiconductor elements 1 a, 1 b, and 1 cand the passive components are buried in the composite resin materiallayer 10.

[0071] It should be noted that a metal wire can be employed to connectthe semiconductor elements to the electrode pattern of the ceramicmultilayer substrate 2. Also, the device of this embodiment can bestructured without the heat release electrode 14 and the interlayerconnector via holes 21. By adopting the cavity portion 2 a as theportion in which the semiconductor elements and the passive componentsare provided, the composite resin material layer 10 is formed easily.

[0072] The invention may be embodied in other forms without departingfrom the spirit or essential characteristics thereof The embodimentsdisclosed in this application are to be considered in all respects asillustrative and not limiting. The scope of the invention is indicatedby the appended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. A high-frequency semiconductor device comprising:a ceramic substrate; an element group including semiconductor elementsand passive components mounted onto a bottom portion of the ceramicsubstrate; and a composite resin material layer formed on the bottomportion of the ceramic substrate so as to bury the element group;wherein the composite resin material layer is formed by a compositeresin material including an epoxy resin and an inorganic fillermaterial, and the composite resin material layer has a flat bottomsurface on which electrodes for connecting to the outside are formed. 2.The high-frequency semiconductor device according to claim 1, whereinthe semiconductor elements are mounted by flip-chip connection.
 3. Thehigh-frequency semiconductor device according to claim 2, whereininterlayer connector structures are formed in the composite resinmaterial layer, the interlayer connector structures being filled with ahigh thermal conductivity resin material having thermal conductivityhigher than that of the epoxy resin, the electrodes for connecting tothe outside include a ground electrode that functions as a heat releaseelectrode, and a surface of the semiconductor elements is connected tothe ground electrode via the interlayer connector structures.
 4. Ahigh-frequency semiconductor device comprising: a first ceramicsubstrate having a circuit pattern; a second ceramic substrate on whichsemiconductor elements are mounted; and a composite resin material layerthat buries the semiconductor elements and is provided between the firstceramic substrate and the second ceramic substrate; wherein thecomposite resin material layer is formed by a composite resin materialincluding an epoxy resin and an inorganic filler material, interlayerconnector structures in which a conducting resin material has beenfilled are formed in the composite resin material layer, and the circuitpattern of the first ceramic substrate and a circuit pattern of thesecond ceramic substrate are electrically connected via the interlayerconnector structures.
 5. The high-frequency semiconductor deviceaccording to claim 4, wherein the semiconductor elements provided on thesecond ceramic substrate are mounted by flip-chip connection.
 6. Thehigh-frequency semiconductor device according to claim 5, wherein atleast one of the semiconductor elements provided on the second ceramicsubstrate is connected by a metal wire.
 7. The high-frequencysemiconductor device according to claim 6, wherein the surroundings ofthe semiconductor elements provided on the second ceramic substrate andconnected by the metal wire are sealed by a liquid epoxy resin.
 8. Ahigh-frequency semiconductor element comprising: a ceramic substratehaving a cavity portion in its bottom portion; an element groupincluding semiconductor elements and passive components mounted to thebottom portion of the cavity portion; a composite resin material layerformed so as to bury the element group in the cavity portion; andelectrodes for connecting to the outside that are formed on a bottomportion of the ceramic substrate other than at the cavity portion;wherein the composite resin material layer is formed by a compositeresin material including an epoxy resin and an inorganic fillermaterial, and a bottom portion of the composite resin material layer isflat in shape.